The invention relates to a method and device for stunning poultry by means of a gas or gas mixture which, at the concentration in which it is present, has the effect of stunning the poultry .
From FR-A-2 334 296 a method and device are known for putting down small mammals, such as cats, puppies, mice, rats and the like. The method comprises placing the mammal to be killed in a first chamber which is open at the top and filled with a gas mixture of oxygen and carbon dioxide for a time which is sufficient to stun the animal. Subsequently, the animal is placed in a second chamber which is open at the top and filled with a high concentration of carbon dioxide for a time which is sufficient to end the life of the animal.
If poultry are to be stunned by means of a gas, one is not inclined to apply methods known for mammals, because of the fact that the respiratory system of poultry is structured differently from that of mammals and is connected to a number of air sacs which are located in the body of poultry and serve to provide buoyancy and body balance control. Said air sacs, which may either be filled with a considerable amount of air or may be empty, are the reason why stunning poultry by means of gas according to the state of the art sometimes takes a relatively long time and in some cases is effected relatively quickly. The resulting unreliability in stunning poultry by means of gas can, of course, be eliminated by continuing the stunning for such a long time that even poultry with a great deal of air in the air sacs can be guaranteed to have been stunned. However, the concomitant shortness of breath and fear reactions are accompanied by severe convulsions. Not only is this a very unpleasant situation for the poultry, but in general this also leads to contusions, fractures or the like, while the quality of the meat of the poultry is adversely affected by the concomitant biochemical immune responses in their body. Incidentally, electrocution, which is traditionally used for stunning poultry, has the same disadvantages.
Moreover, if such a method were to be used on an industrial scale for stunning poultry prior to their slaughter, a vast installation would be required to achieve the long residence time necessary for the poultry in a gas-filled chamber in view of the large numbers of poultry to be processed.
Surprisingly, it was found, however, that the method described above and known for mammals results in quick and reliable stunning when applied to poultry, without discomfort for the poultry, and thus without convulsions.